This invention relates to vent plugs for storage or secondary cells or batteries. More particularly, it relates to vent plugs for eliminating the formation of current conducting electrolyte paths originating at the interior of such cells and terminating at a point on the exterior of the battery having an electrical potential differing substantially from that of the originating point of the electrolyte path.
It may be explained here that typically a rubber gasket is located between the vent plug and the filler or vent neck located at the top of the vent well of a cell or battery. This rubber gasket is provided to form a liquid-tight seal between the vent plug and the vent neck of the battery. Eventually, however, both the upper and lower surfaces of the rubber gasket become wet with electrolyte. This may be caused, for example, during charging of the battery as the electrolyte is agitated and bubbles are formed which upon bursting splash up through the vent well to wet the rubber gasket. As the rubber gasket becomes wet with electrolyte, the electrolyte creeps along the surfaces of the rubber gasket until eventually an electrically conductive current carrying path is established from the plates or element of the cell, the surfaces of the vent well, across the rubber gasket, across the top of the cover of the cell and ultimately to a point or points exterior of the cell of electrical potential differing substantially from that of the originating point of the path so formed, e.g., terminating at an intercell connecter, terminal or metal tray holding the battery.
These electrical paths, formed by such electrolyte creepage, can eventually cause damage to the cell or battery due to electrical shorting of the cell and even result in sparks being generated which may possibly cause fires and explosions.
These potential problems are magnified in multi-cell batteries because of the higher voltages thereof effecting a larger flow of current through such established electrolyte paths. These higher currents can result in large amounts of heat being generated to effect localized combustion of the battery case.
Therefore, in view of the above, a primary object of the invention is to provide vent plugs which prevent the formation of electrically conductive electrolyte leakage paths originating at interior of a cell and terminating at a point of different electrical potential on the surface of the battery.
This and other objects and advantages of the invention will become apparent hereinafter from the following detailed description of the invention.